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Ariel Rokem, Michael Silver; Cholinergic enhancement increases information content of stimulus representations in human visual cortex. Journal of Vision 2014;14(10):1413. doi: https://doi.org/10.1167/14.10.1413.
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Acetylcholine (ACh) plays an important role in cognitive processes such as attention and learning, by modulating neuronal responses in many cortical areas. Electrical stimulation of the basal forebrain (BF), the main source of cortical ACh, increases the reliability of neuronal responses in primary visual cortex of anesthetized rats and decreases redundancy, thereby increasing the information content of stimulus representations (Goard and Dan, 2009). To test the effects of ACh on the fidelity of representations of complex time-varying stimuli in the human brain, we administered the cholinesterase inhibitor donepezil in a double-blind, placebo-controlled crossover design, while measuring fMRI responses to multiple repetitions of a movie segment containing a natural scene. Mutual information between fMRI responses and the stimulus was quantified by decoding the presented stimulus from multi-voxel activity in multiple visual field maps in early visual cortex (V1, V2 and V3). Donepezil administration improved decoding performance, suggesting that ACh enhances the information content of stimulus representations in visual cortex of awake behaving humans. On some presentations of the movie segment, subjects continuously performed a local contrast decrement detection task within either the left or right side of the movie, while maintaining central fixation. This detection task required sustained allocation of visual spatial attention to one hemifield, and this resulted in decreased mutual information between visual cortical activity and the movie stimulus in portions of early visual cortex representing the attended hemifield (e.g., in the right hemisphere, when target detection was performed in the left visual field). That is, decoding performance decreased when visual attention was allocated to the location, but not the features, of the movie stimulus. This decrease in information by spatial attention occurred in both placebo and donepezil sessions.
Meeting abstract presented at VSS 2014
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